Humans perceive sound when things vibrate at a frequency and amplitude that is detectable to them. Frequency is the rate at which things vibrate and corresponds to pitch. It is expressed in hertz, or cycles per second. Musical (or harmonic) sounds vibrate at a regular, periodic rate. Non-musical sounds, such as noise, have more random vibrations. The frequency of the A above middle C on the piano is approximately 440 hertz, for instance. If anything – whether it’s a guitar string or a rubber band – vibrates consistently at that rate, you will sense you are hearing the A above middle C.
Amplitude is the strength of the sound and corresponds to volume. Sometimes the term decibel is used to describe amplitude. A zero decibel sound is undetectable; a 100 decibel sound – like that you’d hear standing near a jet engine – causes pain to one’s ears!
The physical vibrations of an object (i.e. a guitar string or a singer’s vocal chords) cause quick fluctuations in the air molecules around them, producing waves of compressions (molecules bunching up) and rarefactions (molecules expanding) that move through the air. The quicker the vibration, the higher the frequency (or pitch). The stronger the vibration, the greater the swing or fluctuation, and therefore the greater the amplitude or volume.
Amplitude is the strength of the sound and corresponds to volume. Sometimes the term decibel is used to describe amplitude. A zero decibel sound is undetectable; a 100 decibel sound – like that you’d hear standing near a jet engine – causes pain to one’s ears!
The physical vibrations of an object (i.e. a guitar string or a singer’s vocal chords) cause quick fluctuations in the air molecules around them, producing waves of compressions (molecules bunching up) and rarefactions (molecules expanding) that move through the air. The quicker the vibration, the higher the frequency (or pitch). The stronger the vibration, the greater the swing or fluctuation, and therefore the greater the amplitude or volume.
Exploring Sound Waves: Frequency & Amplitude (lynda.com)
PODCAST: The Thing About Rhythm (whatmusicmeans.podomatic.com)
Complex Waveforms: Adding Sine Waves